The present invention relates in general to signal compression-decompression (codec) hardware, and in particular to an semiconductor implementation of novel codec circuitry used for interactive video applications and the like.
As the computer is becoming a more common means of human communication and interaction, the demand is rising for the interaction to be more immediate and complete. This has led to the development of technologies that facilitate interactive video and collaborative video applications such as video conferencing. In most cases, the raw data requirements for such applications far exceed available bandwidth, so data compression is necessary to meet the demand.
Most compression schemes operate on digital images that are expressed as a two-dimensional array of picture elements (pixels) each with one (as in a monochrome or gray-scale image) or more (as in a color image) values assigned to a given pixel. Commonly, a color image is treated as a superposition of three independent monochrome images for purposes of compression.
State-of-the-art compression schemes have been promulgated as standards by an international Motion Picture Experts Group; the current standards are MPEG-1 and MPEG-2. MPEG-1 addresses compressed video bitstream of typically between 0.5 to 1.8 MB/s, while MPEG-2 deals with the faster rates of typically 4 to 9 MB/s. These standards involve more complex compression algorithms based on discrete cosine transform, as well as motion compensation techniques to achieve higher compression ratios with higher resolution. As a result MPEG-based compression-decompression (codec) hardware are considerably more expensive. MPEG-2 for example is primarily intended for broadcast TV, where an encoder with a high price tag (in the range of tens of thousands of dollars) serves multitudes of television viewers each with a set-top box. MPEG is therefore suited for limited applications involving playback of video encoded off-line.
For wider consumer applications such as the PC multimedia market, however, MPEG-based codecs are not only prohibitively expensive, their compression effectiveness is non-optimal, encoding requirements excessive, and scalability too limited. To capture and manipulate images in real time, the affordable alternative to the average PC user remains products that can only perform still frame video capture.
There is therefore a need for a cost-effective image compression-decompression system that enables for example computer users to process a continuous stream of video data in real time.